Volume 127, Issue 2, February 2010
Index of content:
- NOISE: ITS EFFECTS AND CONTROL 
Prediction of the acoustical performance of enclosures using a hybrid statistical energy analysis: Image source model127(2010); http://dx.doi.org/10.1121/1.3273892View Description Hide Description
Enclosures are commonly used to reduce the sound exposure of workers to the noise radiated by machinery. Some acoustic predictive tools ranging from simple analytical tools to sophisticated numerical deterministic models are available to estimate the enclosure acoustical performance. However, simple analytical models are usually valid in limited frequency ranges because of underlying assumptions whereas numerical models are commonly limited to low frequencies. This paper presents a general and simple model for predicting the acoustic performance of large free-standing enclosures which is capable of taking into account the complexity of the enclosure configuration and covering a large frequency range. It is based on the statistical energy analysis (SEA) framework. The sound field inside the enclosure is calculated using the method of image sources. Sound transmission across the various elements of the enclosure is considered in the SEA formalism. The model is evaluated by comparison with existing methods and experimental results. The effect of several parameters such as enclosure geometry, panel materials, presence of noise control treatments, location of the source inside the enclosure, and presence of an opening has been investigated. The comparisons between the model and the experimental results show a good agreement for most of the tested configurations.
127(2010); http://dx.doi.org/10.1121/1.3273890View Description Hide Description
An optimized method is presented for the numerical evaluation of the sound field generated by an incoherent line source, which is commonly used to model road and rail traffic noise. Two different solutions for the numerical integration over the line source are distinguished, a point source solution and a line source solution. With proper segmentation of the line source, both solutions yield accurate results. Special attention is paid to receiver positions close to the (infinite) line through the (finite) line source. At these positions, conventional methods give numerical errors, which occur frequently in calculations of large-scale noise maps of cities, employing automatically generated geographical input data. The problems are avoided by using the optimized method presented here. The method is based on a combination of angular segmentation and linear segmentation of the line source and can be used to minimize the number of point-to-point calculations for noise mapping.
Noise-induced annoyance from transportation noise: Short-term responses to a single noise source in a laboratory127(2010); http://dx.doi.org/10.1121/1.3273896View Description Hide Description
An experimental study was performed to compare the annoyances from civil-aircraft noise, military-aircraft noise, railway noise, and road-traffic noise. Two-way within-subjects designs were applied in this research. Fifty-two subjects, who were naïve listeners, were given various stimuli with varying levels through a headphone in an anechoic chamber. Regardless of the frequency weighting network, even under the same average energy level, civil-aircraft noise was the most annoying, followed by military-aircraft noise, railway noise, and road-traffic noise. In particular, penalties in the time-averaged, -weighted sound level (TAL) of about 8, 5, and 5 dB, respectively, were found in the civil-aircraft, military-aircraft, and railway noises. The reason could be clarified through the high-frequency component and the variability in the level. When people were exposed to sounds with the same maximum -weighted level, a railway bonus of about 3 dB was found. However, transportation noise has been evaluated by the time-averaged -weighted level in most countries. Therefore, in the present situation, the railway bonus is not acceptable for railway vehicles with diesel-electric engines.